Lotus 49-63-72 question

Hi all,
just posted this in the technical area of the forum but a member suggested to try in this section so here it is:

was wondering what was the function of this valve used on Lotus F1s between 1968 and 1971 and hope some tech expert could help.

Lotus 49
http://imageshack.us...6/lotus495.jpg/
Lotus 63
http://imageshack.us...0869fr18a2.jpg/
Lotus 72
http://imageshack.us...tus72r1r21.jpg/

I first thought of a fast refuelling fitting but its the position (no cowling opening near) tells not. Collector pot vent valve??
Thanks in advance for any help!
Gab